In the course of producing oil and gas wells, typically after the well is drilled, the well may be completed. One way to complete a well is to divide the well into several zones and then treat each zone individually.
Treating each section of the well individually may be accomplished in several ways. One way is to assemble a tubular assembly on the surface where the tubular assembly has a series of spaced apart sliding sleeves. Sliding sleeves are typically spaced so that at least one sliding sleeve will be adjacent to each zone. In some instances annular packers may also be spaced apart along the tubular assembly in order to divide the wellbore into the desired number of zones. In other instances when annular packers are not used to divide the wellbore into the desired number of zones the tubular assembly may be cemented in place.
The tubular assembly is then run into the wellbore typically with the sliding sleeves in the closed position. Once the tubular assembly is in place in the well and has been cemented in place or the packers have been actuated the wellbore may be treated.
In other instances a tubular assembly, the casing, is run into the open hole and then cemented into place. The cement and the casing provide zonal isolation. That in order to provide access to the wellbore a plug is run into the well and set below the lowest zone to which access is desired. The perforating gun is then run into the casing and placed adjacent to the producing formation and actuated to puncture the casing. The formation adjacent to the punctures in the casing are then treated by fracturing or other stimulation methods. Another plug is then run into the casing and is placed between the perforations in the casing and the next lowest formation zone. The perforation, stimulation, and plugging processes are repeated until all the zones are treated.
Once all the zones have been treated whether by plug-in per or by opening sliding sleeves and fracturing the plugs or other isolation equipment between the various zones within the casing are removed to allow formation fluid into the interior of the casing and to the surface.
Once the well is on production fluid flows from each of the formations through the adjacent ports or punctures in the casing and to the surface. Unfortunately it is difficult for the operator to determine whether or not fluid is coming from a particular formation, in what quantities it's coming from a particular formation and the quality of the fluid that is coming from a particular formation. The quality of the fluid from a particular formation is usually a function of the ratio of hydrocarbons to water is being produced by particular zone.
By having information related to the fluid production from each zone and operator may enhance the production of a well by closing zones that are either not producing any hydrocarbons or producing fluids having a high ratio of water to hydrocarbon content. Additionally such information would allow an operator to utilize well stimulation or artificial lift techniques at the appropriate stage in the well's life.